Don't turn our law enforcers into thought police

There is a book widely available in Britain that openly incites hatred of gay men. They are, it says, 'an abomination' and 'shall surely be put to death'. The book is Leviticus - a holy text for millions of people worldwide.

It is not a criminal offence to hold that view. But it could be illegal to express it in public if the government amends the law, as it plans to, adding 'hatred on the grounds of sexual orientation' to existing bans on inciting racial and religious hate.

Many secular liberals will support a law that curtails the rights of venomous demagogues, whether fundamentalist clergymen or dance-hall reggae musicians, to sanction murder. Freedom of expression surely does not cover explicit orders to kill.

The problem lies in proving that such an order has been given. In reality, laws against incitement are meant to discourage aggressive rhetoric, symbolise the boundaries of public decency and reinforce taboos on unacceptable language. That places an extraordinary responsibility on courts and police: the power to decide when offensive words are equivalent to criminal deeds.

Two cases last week show how tricky that is. First, on Wednesday, a fundamentalist pressure group lost its battle to bring blasphemy charges against the BBC. The High Court ruled that Christian Voice could not privately prosecute the Corporation for showing Jerry Springer: The Opera, a satire full of irreverent depictions of Christ. The court ruled that broadcasts are immune from blasphemy law.

Then, on Thursday, the Old Bailey convicted Samina Malik, a 23-year-old Muslim woman, of owning terrorist materials. She was given a nine-month suspended sentence for keeping a 'library' of extremist literature. She also wrote bloodthirsty poetry about beheadings, which, the prosecution said, demonstrated her terrorist credentials. Crucially, the court cleared Ms Malik of a more serious charge of 'possessing articles for a terrorist purpose'. In other words, she was guilty of playing with pernicious words, with no evidence that she intended to act on them. One of the pamphlets in her possession, the 'al-Qaeda manual', can be downloaded from the US Department of Justice website.

Had Ms Malik given a public reading of her poetry she could arguably have been liable for prosecution under two different laws: the 2006 Terrorism Act which bans 'glorifying' terrorists and, perversely, the Religious Hatred Act. That was meant to protect Muslims, but it defines hatred 'by reference to religious belief or lack of religious belief'. So calling for the death of non-believers is a crime.

It was on suspicion of inciting religious hate that police earlier this year investigated Channel 4 over a documentary showing British imams denouncing homosexuals. If a 'gay hate' law were enacted, those imams might themselves be liable for prosecution.

At this rate there will be legal scope for the Crown to pursue anyone for expressing any opinion that is deemed offensive by anyone else. The police have been sucked into arbitrating across a range of views with no definition of what is mainstream, what is fringe and what is beyond the pale. The boundaries change, as the obsolescence of blasphemy law shows.

The law is a mess. The government is gradually arrogating the right to define acceptable views. It may have liberal motives - protecting minorities, protecting society from jihadi extremists - but there is a clear danger in this trend. Increasingly, different communities and lobbies will look to the state to define and defend their interests. That diminishes the role of civil society in agreeing a moral consensus, which it should be able to do without constantly invoking legal action.

A democracy must collectively guard itself from those that preach hate. But democracy is itself undermined when we turn law officers into thought police.